Silencer

ABSTRACT

A silencer for attenuating sound coming from a source,having high and low fluid pressure and flow variations is disclosed. The silencer features a housing having an inlet connected to the source, a throat and two divergent branches for the flow of fluid therethrough. A first means coupled to the throat directs fluid pressure and flows from the source to one of the branches and a second means coupled to the throat diametrically opposed to the first means diverts the fluid pressure and flow to the other branch when the pressure in the second means is greater than the fluid pressure and flow at the first means. The second means includes a means for deriving a mean pressure, viz., attenuates peak pressures so that fluid pressure and flow variations at the other one of the divergent branches are reduced.

[. July 24, 1973 SILENCER [76] Inventor: Colin C. Ware, 83 TamarackDrive,

Rochester, N.Y. 14622 [22] Filed: May 22, 1972 [21] Appl. No.: 255,381

Primary Examiner-Richard B. Wilkinson Assistant Examiner-John F.Gonzales Attorney-Samuel R. Genca [5 7] ABSTRACT A silencer forattenuating sound coming from a source,having high and low fluidpressure and flow variations is disclosed. The silencer features ahousing having an inlet connected to the source, a throat and twodivergent branches for the flow of fluid therethrough. A first meanscoupled to the throat directs fluid pressure and flows from the sourceto one of the branches and a second means coupled to the throatdiametrically opposed to the first means diverts the fluid pressure andflow to the other branch when the pressure in the second means isgreater than the fluid pressure and flow at the first means. The secondmeans includes a means for deriving a mean pressure, viz., attenuatespeak pressures so that fluid pressure and flow variations at the otherone of the divergent branches are reduced.

12 Claims, 9 Drawing Figures PAIENIEQJUM 3.741. 70 1 SHEET 1 0F 2 Fig. 4

PATENIEDJULZMQTS SHEET 2 BF 2 42 Fig. 6

SILENCER BACKGROUND OF THE INVENTION I. Field of Invention The presentinvention relates to an anti-pollution device and more particularly tosilencers.

2. Prior Art Although the present invention is suited for more generalapplications such as devices for suppressing fluid pulsations, pressureand flow variations from a source, it is particularly adapted for use inan internal combustion engine exhaust system such as but not limited tomuffling of exhaust noise. Mufflers and resonators for internalcombustion engines are well known to those skilled in the art. Whileprior art mufflers and resonators have been satisfactory for theirintended purpose, problems of noise suppression still exist anddischarge of pollutents in the atmosphere is still prevalent with thesedevices. Accordingly, there is a pressing need for a silencer that willnot only suppress noise but will also reduce pollution.

SUMMARY OF THE INVENTION Briefly described, a silencer in accordancewith a preferred embodiment of the invention includes a housing havingan inlet for receiving a pulsating fluid from a source having high andlow fluid pressures and flow variations and two divergent branches forthe flow of fluid therethrough. The housing has'a throat regioninterposed between the inlet and the two divergent branches. A firstmeans is disposed at the throat for directing the fluid pressure andflow to one of the branches and a second means is connected between thethroat and the one branch for diverting the fluid pressure and flowvariations to the other'branch only when the pressure in the secondmeans is greater than the fluid pressure at the first means in thethroat. The second means includes an attenuator for deriving a meanpressure or pressure lower than a peak pressure therein so that peakpressures which are higher than the mean pressure on the above saidlower pressure in the attenuator are directed into the attenuatorthrough the first branch and when the fluid pressure or flow variationsfrom the source are lower than the pressure in the attenuator, the fluidpressure and flow variations at the throat are directed to the otherbranch. In other words, the fluid pressures and flow variations from thesource which are in effect alternating variations are reduced to asubstantially constant level, thus suppressing noise.

DESCRIPTION OF THE DRAWINGS The invention both as to its organizationand method of operation, will best be understood by reference to thefollowing description taken in connection with the accompanying drawingsin which:

FIG. I is a longitudinal sectional view of a silencer embodying thefeatures of the invention;

FIG. 2 is a graph relating fluid pressure and flow variation from asource such as an internal combustion engine;

FIG. 3 isa side view of a motor vehicle exhaust system showing that asilencer made in accordance with FIG. 5 is a longitudinal sectional viewof a silencer made in accordance with a preferred embodiment of theinvention;

FIG. 6 is a longitudinal sectional view of another silencer made inaccordance with the invention;

FIG. 7 is a longitudinal sectional view of yet another silencer made inaccordance with the invention;

FIG. 8 is a cross-sectional view of the silencer shown in FIG. 5 takenalong line 8-8;

FIG. 9 is a fragmentary cross-sectional view of the silencer similar tothe silencer in FIG. 5 only disposed at the manifold section of theengine.

DETAILED DESCRIPTION Referring to the drawings, there are shown variousembodiments of the invention in silencers which are not only suited forother applications as stated above, but which are particularly adaptedfor internal combustion engines such as shown at l. The engine 1 whenoperating on fuel such as gas or oil, discharges exhaust gases from eachcylinder, one of which is partly shown at 2 (FIG. 9) after each burningof fuel within the cylinder 2. The exhaust gases bypass an exhaust valve3 through exhaust port 4. In accordance with the invention, a SILENCER90 may be coupled to the engine 1 at exhaust port 4 and 5 which isgenerally the region in which a conventional exhaust manifold may beassembled to the internal combustion engine 1. If desired, however, theSILENCER may be installed at another location such as at 7 with respectto engine 1, for. example, SILENCER 10 (FIG. 10);SILENCER 40 (FIG. 4);SILENCER 50' (FIG. 5); SILENCER 60 (FIG. 6) or SI- LENCER (FIG. 7) maybe employed to silence exhaust noise at port 4 by a connection from theengine at the manifoldregionat 5 by exhaust pipe 6. Thus the presentinvention is interchangeable with present mufflers which are usuallylocated at 7 to suppress noise.

Those skilled in the art will appreciate the above mentioned componentsof the engine I and their operation. It is also well known to thoseskilled in the art that engine 1 when operating, exhaust carbon dioxide,carbon monoxide, hydrocarbons and other pollutants through the exhaustport 4 as well as noise. The engine 12 generates sound waves at theexhaust port 4 having a frequency that is a function of the engine speed(revolutions per minute) and the number of combustion cylinders 2. Thisfrequency is sometimes referred to as the firing frequency and isillustrated by the curves 21, 22 illustrated in FIG. 2. The curves 21,22 are representative of the firing and exhausting frequency and eachpeak 23, 24 of curves 2], 22 respectively, indicates an exhausting froma cylinder 2. Curve 21 represents fluid inlet pressure with a time basewhile curve 22 represents inlet fluid flow eith the same time base, bothof which happen to have the same frequency for the internal combustionengine 1. Horizontal line 25 incurve 21 is the mean or average pressurewhile the horizontal line 26 is the average flow of the curve22.

Referring first to FIG. 1, a SILENCER 10 in accordance with theinvention is shown. The SILENCER 10 includes an inlet at I1 and twodivergent branches 12, I3 and a throat region at I4. The throat regionis preferably a venturi having a uniformly converging section to areduced cross-sectional area and adiverging section expanding towardsthe divergent branches 1 2 and 13.

Branch 13 is connected to a pipe 15 to an outlet 16. Divergent branch 12is connected to an attenuator 17 in which peak pressure and flow areattenuated and mean pressure or lower pressure than the peak pressure isderived. Connected between the attenuator 17 and an attenuator port 18at the throat region 14 is a tube or pipe 19 for directing pressure fromthe attenuator 17 to the attenuator port 18 substantially normal to theflow of gases in the throat region 14. This tube or pipe 19 may have alength equal to one quarter wave length of the operating or firingfrequency of the engine 1. Fluid pressure and flow at the inlet 11 issensed by a tube or pipe 9 connected between the inlet 11 and a port 20at the throat region 14. This tube or pipe 9 is also in the order of onequarter wave length of the operating frequency of the engine 1. The port20 is diametrically opposed to the attenuator port 18 and the flow ofgases from the port 20 is also substantially normal to flow of gases inthe throat region 14. The length of tube 9, 19 is not restricting.

In the operation of the SILENCER 10, exhaust gases having fluid pressureand flow variations such as the type emitted from the source or theengine 1 are admitted at inlet 11 and travel down the throat region 14and at the same time travel in tube or pipe 90 in phase with the exhaustgas traveling within the throat region 14. If the pressure or flowwithin attenuation port 18 is less than the pressure or flow at port 20,exhaust gases are directed towards divergent branch 12 and intoattenuator 17. The exhaust gases in the attenuator 17 are allowed toexpand and a reduction pressure is achieved in the attenuator 17. Thisreduced pressure in the attenuator 17 may be the mean of averagepressure 26 or flow as shown in the curves 21 and 22 respectively inFIG. 2. The reduced pressure in the attenuator 17 is sensed by the tubeor pipe 19 and this reduced pressure or flow is fed back into the throatregion 14 in a substantially normal direction to the gases flowing inthe throat region 14, and if the pressure or flow at port 20 is lessthan the pressure or flow at attenuator port 18, the exhaust gases aredirected to divergent branch 13 and are exhausted to the atmospherethrough pipe 15 and outlet 16. Since exhaust gases flowing within thethroat region 14 do have flow and pressure variation, the gases may bedirected to either one of the divergent branches 12, 13 as a function ofthe diametrical flow or pressures at ports 18 and 20. The diametricalpressures are a function of the flow and pressure variations of theexhaust gases. The maximum pressure and flow in the attenuator 17 cannotbe greater than .peak pressure of the exhaust gases from the engine 1because any higher pressure or flow than peak pressure in the branch 12will direct flow and pressure to divergent branch 13. The peak pressure23 and flow 24 will normally be directed to branch 12 and attenuator l7and be attenuated or reduced therein when pressure and flow at port 20is greater than flow at port 18. The effective reduced or averagepressure in the attenuator l7 and at port 18 however may be greater thanpressure or flow in the throat region 14 and port 20 so that the exhaustgases in the throat region 14 will be directed to the divergent branch13 and exhausted through pipe and outlet 16. As was mentioned earlier,the exhaust gases in the throat 14 the port 20 are in phase with eachother and therefore it may now be seen that the peak pressures and floware chopped by the attenuator 17 and energy as shown by cross-section at28 of curve 22 is shifted in phase and dumped into the shaded area 29 ofcurve 22 so that the resultant pressure and flow waves shown by curves21, 22 (FIG. 2) is in effect substantially a straight line illustratedas an average or mean pressure at 26. Thus, pressure and fluid flowvariations are reduced or substantially eliminated by the SI- LENCER 10to suppress noise.

While the operation of the SILENCER 10 has been described by the use ofexhaust gases from a source or engine 1, it should be understood thatthe invention will also function in the same manner for fluids havingsound waves since such waves are alterations in pressure and particledisplacement and may be shifted to the divergent branches l2 and 13 as afunction of the relative pressures at ports 20 and 18 and then mayeither be discharged or attenuated to derive a steady state conditionwithout objectionable variations.

Referring now to FIGS. 4 to 9, various embodiments of the invention areshown in SILENCERS 40, 50, 60, and 90. These SILENCERS 40, 50, 60, 70and are of similar construction; accordingly, like elements andstructures will have designations and reference numerals which arealike.

The SILENCER 40 may be connected to the engine 1 by 7 by a pipe 6 (FIG.3), at inlet 41. The SILENCER 40 is similar to the SILENCER 10, exceptthat the attenuator 42 for the SILENCER is a wrap around attenuator 42instead of being a closed end attenuator 17 as shown in FIG. 1. The wraparound attenuator 42 provides a more compact SILENCER 40 than the SI-LENCER 10. The attenuator 42 includes end caps 36, 37 in sealingrelationship with a wrap around member 35, inlet 41 and outlet 38. TheSILENCER 40 includes divergent branches 43, 44 and a throat region 45interposed between the inlet 41 and the divergent branches 43, 44. Thethroat region 45 is similar to throat region 14 of the SILENCER l0 andis a venturi. Pressure at the inlet 41 is sensed by a tube or pipe 46terminating at port 47. The length of the tube or pipe 46 is less than aquarter wave length of the operating frequency of the engine 1. The port47 at the throat 45 has a crosssection area equal to about one third ofthe crosssection of the cross-sectional area of throat region 45 at thesmallest cross-section of the throat 45. However, this is not a limitingcondition and may be varied if desired without departing from theinvention. The pressure or flow at port 47 is directed normal to theflow of fluid in the throat 45. The divergent branch 44 is coupled tothe attenuator 42 which functions similar to the attenuator 17 exceptthat a baffle 48 is included to divert fluid flow and pressure wavesentering the attenuator 42 and also for stopping reflected pressure andflow from re-entering the branch 44. Pressure in the attenuator 42 issenses at the tube or pipe 49 which is connected to attenuator port 39.The attenuator port 39 is diametrically opposed to port 47 and may be ofthe same size as port 47. Pressure and flow at the port 39 is normal tothe flow of fluid in the throat region 45. Divergent branch 43 isconnected to an outlet 38.

The operation of the SILENCER 40 is similar to the operation of theSILENCER 10 except that the attenuator is wrapped around the throatregion 45 and accordingly, operates at a slightly higher temperature.Also, the SILENCER 40 includes a baffle 48 disposed proximal to thedivergent branch 44 not only for directing fluid flow and pressuretheoughout the attenuator but also for preventing a reflection orbouncing back of fluid flow or pressure.

Assuming for purposes of describing the operation of the SILENCER 40,the exhaust gases from the engine I are pulsating in a manner similar tothe wave form 21 shown in FIG. 2 and are applied to inlet 41. Each ofthe pressure peaks 23 occur at an exhaust of gas from the cylinder 2while the valleys between the peaks are between firing time so that thepressure curve 21 is a function of time. The exhaust gases entering theinlet 41 are passed to the throat region 45 directly and at the. sametime and in phase so that a peak pressure 23 will be present at thethroat region 45 and at port 47 since the peak pressure was sensedthrough tube. 46. Assume also that there is a relatively low pressure atport 49 and attenuator 42 and the pressure tube 46 and port 47 willdirect the exhaust gas therein normal to the flow of exhaust gases inthe throat region 45 so that the resultant flow of the exhaust gases istowards the divergent branch 44 and attenuator 42.

A study of vector analysis will show that when two flows areperpendicular to each other, the gases will travel in a resultantdirection into the divergent branch 44 and thence into the attenuator42. The gases in the attenuator will expand and be directed by thebaffle 48 throughout the attenuator 42. At the same time, the pressurein the attenuator will increase and be applied to port 39 by tube 49. Ifthe pressure at 39 is greater than the pressure at port 47, the exhaustgases will be directed towards branch 43 and exhausted through outlet38. However if the pressure at port 39 is still less than the pressureat port 47, the gases will continue to be directed to divergent branch44 until the pressures at ports 39 and 47 are equal at which time theexhaust gases may be directed to both of the divergent branches 43, 44.

In effect then, peak pressure 23 is directed to the attenuator 42 wherethey are attenuated or chopped and shifted in phase between the nextpeak pressure as more particularly shown in FIG. 2 where the flow 28 andenergy content is dumped into the valley to raise its pressure andenergy as shown by the shaded area 29,

thereby reducing the pressure in the attenuator.

THE PREFERRED EMBODIMENT Referring now to FIGS. and 8, a SILENCER 50 inaccordance with a preferred embodiment of the invention is shown. TheSILENCER 50 is similar to the SI- LENCER 40 except that the sensingtubes or pipes 46 and 49 and ports 47 and 39 respectively areeliminated. Instead a new throat region 51 is employed having the sameeffectiveness as the ports 39 and 47.

A header port 52 is disposed at approximately the same place as port 47and directs fluid flow and pressure to branch 44 while another headerport 53 directs fluid pressure and flow to the branch 43 when thedifferential pressures thereat are appropriate in a manner to bedescribed hereinafter. The throat region 51 of the SILENCER 50 isrectangular as shown in FIG. 8 and is a venturi having a smallercross-sectional area proximal to header ports 52 and 53 and expandstherefrom into divergent branches 43, 44. The remaining components andelements of the SILENCER 50 are similar to corresponding components andelements of the SILENCER 40 and are similarly numbered as previouslystated.

In the operation of the SILENCER 50, exhaust gases are directed to thethroat 51 from inlet 41. The exhaust gases as described before have thesame waveform and. as a consequence, each pressure peak 23 coming incontact with header port 52 directs pressure normal to the exhaust gasestraveling through the throat 51 so that a result flow of exhaust gasesisdirected to attenuator 42. To further assist the flow of gases to theattenuator, the header port 53 may have a low pressure thereat when the.pressure 52. is at or near a peak pressure. However, when the pressurein the attenuator 42 increases and approaches peak pressure, the headerport 53 in cooperation with the pressure in the attenua: tor 42 directsthe flow of gases to branch 43 and outlet 38.

The SILENCER 90 of FIG. 9 is similar to the SI- LENCER 50 except that itis connected to the engine 1 at 5 and it includes an attenuator 92 whichis structurally and functionally similar except that it has arectangular cross-section and is used in common with other SILENCER 90and thus also serves as an exhaust manifold for the engine 1.

Referring now to FIGS. 6 and 7, SILENCERS 60 and 70 are shown. TheseSILENCERS 60, 70 are similar to SILENCER 50 of the preferred embodimentof the invention.

SILENCER 60 is similar to SILENCER 50 except that it includes a throatregion 61 having the sensing tube and port 39 of the SILENCER (FIG. 4).SI- LENCER 70 is similar to SILENCER 50 except that it includes a throatregion having the sensing tube or pipe 46* and port 47. It will be seenthat in principle, the exhaust gases flowing through the throat region61 or 71 of SILENCERS 60, 70 respectively will be directed to one of thedivergent branches 43 or 44 depending upon the differentially opposedpressures acting normal to the transverse flow of exhaust gases throughthe throat, which differential pressures are presented by the headerports 52 and 53 or ports 39 and 47 as a combination of the ports and-port headers. The SILENCER 60 also includes another baffle 62 in theattenuator 42 to dispurse and achieve a mean pressure in the attenuator42.

In the operation of the SILENCER 60, exhaust gases are admitted at theinlet 41 and are accelerated at the venturi throat region 61 whence theheader port 52 directs the exhaust gases to the divergent branch 44since the normal pressure acting on the transverse gases flowing throughthe throat region 61 is higher at 52 than at 39. From the branch 44, thegases enter the attenuator 42 and are expanded therein. The tube 49senses the pressure in the attenuator 42 and the pressure in theattenuator 42 is present at 39 when it acts normal to the flowing ofexhaust gases through the throat region 61. Now if the pressure at port39 is greater than the pressure at header port 52, the exhaust gaseswill be directed to the divergent branch 43 and through outlet 38.However, if the pressure'at port 39 is less than the pressure at headerport 52, the exhaust gases will be directed towards the branch 44 aspreviously stated. If the pressure at port 39 and header port 52 areequal, the gases will flow in the path of least resistance, namely,through branch 43 and outlet 38. It may now be seen in the SILENCERS 10,40, 50, 60, and that the pressure in the attenuator is a floatingreference pressure which adjusts to conditions and levels the fluid flowand pressure variations to reduce or suppress noise.

The SILENCER 70 operates in a manner similar to the SlLENCERS 10, 40,50, 60, 90 and functions in a similar manner, that is the difference inpressure at header port 53 and port 47 controls the flow of fluid, gasesand liquids automatically to the attenuator 42 or to the outlet 38 asjust described.

The divergent branches 43, 44 may be symmetrical or assymmetrical withrespect to the longitudinal axis of the throat regions 51, 61, 71 of theSILENCERS S0, 60, 70 respectively to controlthe amount of flow to outlet38 or attenuator 42.

While specific embodiments of the invention have been desc-ibed andshown, these may be considered illustrative. Still further modificationswill undoubtedly occur to those skilled in the art. Therefore, theforegoing description is to be considered as illustrative and not in anylimiting sense.

What is claimed is:

l. A silencer comprising:

a. a housing having an inlet for receiving a fluid having high and lowfluid pressure and flow variations and at least two divergent branches,

b. said housing having a throat region interposed between said inlet andsaid two divergent branches,

- c. first means disposed at said throat for directing said fluidpressure and flow to one of said branches, and

(1. second means connected between said throat and said one branch fordiverting said fluid pressure and flow variations to said other branchwhen the pressure in said second means is greater than said fluidpressure at said first means in said throat.

2. The invention defined in claim 1 wherein said second means includesattenuation means for deriving a mean pressure therein.

3. The invention defined in claim 1 wherein said second means includesmeans for reducing said fluid pressure and flow variations.

4. The invention defined in claim 1 wherein said second means includesan attenuator.

S. The invention defined in claim 1 wherein said throat region isrelatively long.

6. The invention defined in claim 1 wherein said throat region isrelatively short.

7. The invention defined in claim 1 wherein said throat is a venturi.

8. The invention defined in claim 1 wherein said divergent branchesdiverge along a symmetrical axis of said throat region.

9. The invention defined in claim 1 wherein said divergent branchesdiverge along an asymmetrical axis of said throat region.

10. The invention defined in claim 1 wherein said second means includesa deflector means disposed proximal to said one divergent branch fordiverting re flected pressure waves within said second means whenpresent.

11. The invention defined in claim 1 wherein said second means isdiametrically opposed to said first means in said throat region.

12. The invention defined in claim 1 wherein said first and second meansare fixed in cooperative relationship to each other and said throatregion.

1. A silencer comprising: a. a housing having an inlet for receiving afluid having high and low fluid pressure and flow variations and atleast two divergent branches, b. said housing having a throat regioninterposed between said inlet and said two divergent branches, c. firstmeans disposed at said throat for directing said fluid pressure and flowto one of said branches, and d. second means connected between saidthroat and said one branch for diverting said fluid pressure and flowvariations to said other branch when the pressure in said second meansis greater than said fluid pressure at said first means in said throat.2. The invention defined in claim 1 wherein said second means includesattenuation means for deriving a mean pressure therein.
 3. The inventiondefined in claim 1 wherein said second means includes means for reducingsaid fluid pressure and flow variations.
 4. The invention defined inclaim 1 wherein said second means includes an attenuator.
 5. Theinvention defined in claim 1 wherein said throat region is relativelylong.
 6. The invention defined in claim 1 wherein said throat region isrelatively short.
 7. The invention defined in claim 1 wherein saidthroat is a venturi.
 8. The invention defined in cLaim 1 wherein saiddivergent branches diverge along a symmetrical axis of said throatregion.
 9. The invention defined in claim 1 wherein said divergentbranches diverge along an asymmetrical axis of said throat region. 10.The invention defined in claim 1 wherein said second means includes adeflector means disposed proximal to said one divergent branch fordiverting reflected pressure waves within said second means whenpresent.
 11. The invention defined in claim 1 wherein said second meansis diametrically opposed to said first means in said throat region. 12.The invention defined in claim 1 wherein said first and second means arefixed in cooperative relationship to each other and said throat region.